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Metalworking
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Machining a bar of metal on a lathe.Metalworking is the craft and
practice of working with metals to create individual parts,
assemblies, or large scale structures. The term covers a wide range of
work from large ships, bridges and oil refineries to delicate
jewellery. It therefore includes a correspondingly wide range of
skills and the use of many different types of metalworking processes
and their related tools.

Metalworking is an art, hobby, industry, and trade. It relates to
metallurgy, a science, jewellery making, an art-and-craft, and as a
trade and industry with ancient roots spanning all cultures and
civilizations. Metalworking had its beginnings millennia in the past.
At some imprecise point in the distant past humankind discovered that
certain rocks now called ores could be smelted, producing metal.
Further, they discovered that the metal product was malleable and
ductile and thus able to be formed into various tools, adornments and
put to other practical uses. Humans over the millennia learned to work
raw metals into objects of art, adornment, practicality, trade, and
engineering.

Contents [hide]
1 Prehistory
2 History
3 General metalworking processes
3.1 Forming processes
3.1.1 Casting
3.1.2 Plastic deforming
3.1.3 Powder forming
3.1.4 Sheet metal forming
3.2 Cutting processes
3.2.1 Cutting
3.2.2 Milling
3.2.3 Turning and threading
3.2.4 Drilling and tapping
3.2.5 Grinding
3.2.6 Filing
3.2.7 Broaching
3.3 Joining processes
3.3.1 Welding
3.3.2 Brazing
3.3.3 Soldering
4 Preparation and validation
4.1 Marking out
5 See also
6 Notes
7 References
8 External links



[edit] Prehistory
Metalworking predates history. No one knows with any certainty where
or when metalworking began. The earliest technologies were impermanent
to say the least and were unlikely to leave any evidence for long. The
advance that brought metal into focus was the connection of fire and
metals. Who accomplished this is as unknown as the when and where.

Not all metal required fire to obtain it or work it. Isaac Asimov
speculated that gold was the "first metal."[1] His reasoning is that
gold by its chemistry is found in nature as nuggets of pure gold. In
other words, only gold, as rare as it is, is found in nature as the
metal that it is. There are a few exceptions as a result of meteors.
All other metals are found in ores, a mineral bearing rock, that
require heat or some other process to liberate the metal. Another
feature of gold is that it is workable as it is found, meaning that no
technology beyond eyes to find a nugget and a hammer and an anvil to
work the metal is needed. Stone hammer and stone anvil will suffice
for technology. This is the result of gold's properties of
malleability and ductility. The earliest tools were stone, bone, wood,
and sinew. They sufficed to work gold.

At some unknown point the connection between heat and the liberation
of metals from rock became clear, rocks rich in copper, tin, and lead
came into demand. These ores were mined where ever they were
recognized. Remnants of such ancient mines have been found all over
what is today the Middle East.[2] Metalworking was being carried out
by the South Asian inhabitants of Mehrgarh between 7000€“3300 BCE.[3]
The end of the beginning of metalworking occurs sometime around 6000
BCE when copper smelting became common in the Middle East.

The ancients knew of seven metals. Here they are arranged in order of
their oxidation potential:

Iron +0.44,
Tin +0.14
Lead +0.13
Copper -0.34
Mercury -0.79
Silver -0.80
Gold -1.50
The oxidation potential is important because it is one indicator of
how tightly bound to the ore the metal is likely to be. As can be
seen, iron is significantly higher than the other six metals while
gold is dramatically lower than the six above it. Gold's low oxidation
is one of the main reasons that gold is found in nuggets. These
nuggets are relatively pure gold and are workable as they are found.

Copper ore, being relatively abundant, and tin ore became the next
important players in the story of metalworking. Using heat to smelt
copper from ore, a great deal of copper was produced. It was used for
both jewelry and simple tools. However, copper by itself was too soft
for tools requiring edges and stiffness. At some point tin was added
into the molten copper and bronze was born. Bronze is an alloy of
copper and tin. Bronze was an important advance because it had the
edge-durability and stiffness that pure copper lacked. Until the
advent of iron, bronze was the most advanced metal for tools and
weapons in common use.

Looking beyond the Middle East, these same advances and materials were
being discovered and used the world around. China and Britain jumped
into the use of bronze with little time being devoted to copper. Japan
began the use of bronze and iron almost simultaneously. In the new
world things were different. Although the peoples of the New World
knew of metals, it wasn't until the arrival of Europeans that metal
for tools and weapons took off. Jewelry and art were the principal
uses of metals in the New World prior to European influence.

Around the date 2700 BCE, production of bronze was common in locales
where the necessary materials could be assembled for smelting,
heating, and working the metal. Iron was beginning to be smelted. Iron
began its emergence as an important metal for tools and weapons. The
Iron Age was dawning.


[edit] History

Turret lathe operator machining parts for transport planes at the
Consolidated Aircraft Corporation plant, Fort Worth, Texas, USA in the
1940s.By the historical periods of the Pharaohs in Egypt, the Vedic
Kings in India, the Tribes of Israel, and the Mayan Civilization in
North America, among other ancient populations, precious metals began
to have value attached to them. In some cases rules for ownership,
distribution, and trade were created, enforced, and agreed upon by the
respective peoples. By the above periods metalworkers were very
skilled at creating objects of adornment, religious artifacts, and
trade instruments of precious metals (non-ferrous), as well as
weaponry usually of ferrous metals and/or alloys. These skills were
finely honed and well executed. The techniques were practiced by
artisans, blacksmiths, atharvavedic practitioners, alchemists, and
other categories of metalworkers around the globe. For example, the
ancient technique of granulation is found around the world in numerous
ancient cultures before the historic record shows people traveled seas
or overland to far regions of the earth to share this process that
still being used by metalsmiths today.

As time progressed metal objects became more common, and ever more
complex. The need to further acquire and work metals grew in
importance. Skills related to extracting metal ores from the earth
began to evolve, and metalsmiths became more knowledgeable.
Metalsmiths became important members of society. Fates and economies
of entire civilizations were greatly affected by the availability of
metals and metalsmiths. Today modern mining practices are more
efficient, but more damaging to the earth and to the workers that are
engaged in the industry. Those that finance the operations are driven
by profits per ounce of extracted precious metals. The metalworker
depends on the extraction of precious metals to make jewellery, build
more efficient electronics, and for industrial and technological
applications from construction to shipping containers to rail, and air
transport. Without metals, goods and services would cease to move
around the globe on the scale we know today.

More individuals than ever before are learning metalworking as a
creative outlet in the forms of jewellery making, hobby restoration of
aircraft and cars, blacksmithing, tinsmithing, tinkering, and in other
art and craft pursuits. Trade schools continue to teach welding in all
of its forms, and there is a proliferation of schools of Lapidary and
Jewelers arts and sciences at this- the beginning of the 21st Century
AD.


[edit] General metalworking processes
Metalworking generally is divided into the following categories,
forming, cutting, and, joining. Each of these categories contain
various processes.


[edit] Forming processes
These processes modify the shape of the object being formed by
deforming the object, that is, without removing any material.

Forming is a collection of processes wherein the metal is rearranged
into a specified geometry (shape) by:

heating until molten, poured into a mold, and cooled,
heating until the metal becomes plastically deformable by application
of mechanical force,
by the simple application of mechanical force.
Casting is an example of achieving a specific form by pouring molten
metal into a mold and allowing it to cool. Hot forging is an example
of moving heated metal into a specific form by deforming it with tools
such as hammers or hydraulic presses while the material is at forging
temperature. Drawing copper wire to a specific size is an example of
forming by the use of mechanical tooling and mechanical force.


[edit] Casting

A sand casting mold.Sand casting
Shell casting
Investment casting (called lost wax casting in art)
Die casting
Spin casting

[edit] Plastic deforming

A red-hot metal workpiece is inserted into a forging press.Forging
Rolling
Extrusion
Spinning
Stamping
Raising

[edit] Powder forming
Sintering

[edit] Sheet metal forming

A metal spun brass vase.Main article: Sheet metal forming
Bending :A calculated deformation of the metal from its original
shape.
Drawing
Pressing
Spinning
Flow turning
Roll forming
Wheeling using an English wheel (Wheeling machine)

[edit] Cutting processes

[edit] Cutting

A CNC plasma cutting machining.Main article: Machining
Cutting is a collection of processes wherein material is brought to a
specified geometry by removing excess material using various kinds of
tooling leaving a finished part matching a set of specifications. The
net result of cutting is two products, the waste or excess material,
and the finished part. If this was a discussion of woodworking, the
waste would be sawdust and excess wood. In cutting metals the waste is
chips or swarf and excess metal. These processes can be divided into
chip producing cutting, generally known as machining. Burning or
cutting with an oxyfuel torch is a welding process not machining.
There are also miscellaneous specialty processes such as chemical
milling.

Cutting is nearly fully represented by:

Chip producing processes most commonly known as machining
Burning, a set of processes which cut by oxidizing a kerf to separate
pieces of metal
Specialty processes
Drilling a hole in a metal part is the most common example of a chip
producing process. Using an oxy-fuel cutting torch to separate a plate
of steel into smaller pieces is an example of burning. Chemical
milling is an example of a specialty process that removes excess
material by the use of etching chemicals and masking chemicals.

There are many technologies available to cut metal.

Manual technologies: saw, chisel, shear or snips
Machine technologies: turning, milling, drilling, grinding, sawing
Welding/burning technologies: burning by laser, oxy-fuel burning, and
plasma
Erosion technologies:by water jet or electric discharge.
Cutting fluid or coolant is used where there is significant friction
and heat at the cutting interface between a cutter such as a drill or
an end mill and the workpiece. Coolant is generally introduced by a
spray across the face of the tool and workpiece to decrease friction
and temperature at the cutting tool/workpiece interface to prevent
excessive tool wear. In practice there are many methods of delivering
coolant.


[edit] Milling
Main article: Milling machine

A milling machine.Milling is the complex shaping of metal (or possibly
other materials) parts, by removing unneeded material to form the
final shape. It is generally done on a milling machine, a power-driven
machine that in its basic form is comprised of a milling cutter that
rotates about the spindle axis (like a drill), and a worktable that
can move in multiple directions (usually three dimensions [x,y,z axis]
relative to the workpiece, whereas a drill can only move in one
dimension [z axis] while cutting). The motion across the surface of
the workpiece is usually accomplished by moving the table on which the
workpiece is mounted, in the x and y directions. Milling machines may
be operated manually or under computer numerical control (CNC), and
can perform a vast number of complex operations, such as slot cutting,
planing, drilling and threading, rabbeting, routing, etc. Two common
types of millers are the horizontal miller and vertical miller.


[edit] Turning and threading
Main article: Lathe (metal)

A lathe cutting material from a workpiece.A lathe is a machine tool
which spins a block of material so that when abrasive, cutting, or
deformation tools are applied to the workpiece, it can be shaped to
produce an object which has rotational symmetry about an axis of
rotation, called Solids of Revolution. Examples of objects that can be
produced on a lathe include candlestick holders, table legs, bowls,
baseball bats, crankshafts or camshafts.

The material may be held in place by a chuck or worked between one or
two centers of which at least one can be moved horizontally to
accommodate varying material lengths. In a metalworking lathe, metal
is removed from the workpiece using a hardened cutting tool which is
usually fixed to a solid moveable mounting called the "toolpost", this
arrangement is then moved around the workpiece using handwheels and/or
computer controlled motors. The main difference between the Milling
Machine and the Lathe is that in the Milling Machine the tool is
moving but in the Lathe, the work is moving. Modern CNC lathes can do
secondary operations like milling in X,Y,Z direction by using driven
tools also called live tools. When driven tools are used the work
piece stops rotating and the driven tool executes the machining
operation with a rotating cutting tool. Driven tools increase
machining performance as all operations can be made in one set up in
the CNC lathe.


[edit] Drilling and tapping
Main article: Drilling and threading

Three different types and sizes of tapsDrilling is the process of
using a drill bit in a drill to produce holes. Under normal usage,
swarf is carried up and away from the tip of the drill bit by the
fluting. The continued production of chips from the cutting edges
pushes the older chips outwards from the hole. This continues until
the chips pack too tightly, either because of deeper than normal holes
or insufficient backing off (removing the drill slightly [breaking the
chip] or totally from the hole [clearing the bit] while drilling).
Lubricants (or coolants) (i.e. cutting fluid) are sometimes used to
ease this problem and to prolong the tool's life by cooling,
lubricating the tip and improving chip flow.

Taps and dies are tools commonly used for the cutting of screw threads
in metal parts. A tap is used to cut a female thread on the inside
surface of a pre-drilled hole, while a die cuts a male thread on a
preformed cylindrical rod.


[edit] Grinding
Main article: Grinding machine
Main article: Abrasive machining

A surface grinder in action.Grinding uses an abrasive process to
remove material from the workpiece. A grinding machine is a machine
tool used for producing very fine finishes, making very light cuts, or
high precision forms using a abrasive wheel as the cutting device.
This wheel can be made up of various sizes and types of stones,
diamonds or inorganic materials.

The simplest grinder is a bench grinder or a hand-held angle grinder,
for deburring parts or cutting metal with a zip-disc.

Grinders have increased in size and complexity with advances in time
and technology. From the old days of a manual toolroom grinder
sharpening endmills for a production shop, to today's 30000rpm CNC
auto-loading manufacturing cell producing jet turbines, grinding
processes vary greatly.

Grinders need to be very rigid machines to produce the required
finish. Some grinders are even used to produce glass scales for
positioning CNC machine axis. the common rule is the machines used to
produce scales be 10 times more accurate than the machines the parts
are produced for.

In the past grinders were used for finishing operations only because
of limitations of tooling. Modern grinding wheel materials and the use
of industrial diamonds or other made-made coatings (cubic boron
nitride) on wheel forms have allowed grinders to achieve excellent
results in production environments instead of being relegated to the
back of the shop.

Modern technology has advanced grinding operations to include CNC
controls, high material removal rates with high precision, lending
itself well to aerospace applications and high volume production runs
of precision components.


[edit] Filing
Main article: Filing (metalworking)
Filing is combination of grinding and saw tooth cutting using a file.
It is usually used in the deburring process.


[edit] Broaching
Main article: Broach (metalworking)
Broaching is machining operation used to cut keyways into shafts.


[edit] Joining processes

[edit] Welding
Main article: Welding

Mig weldingWelding is a fabrication process that joins materials,
usually metals or thermoplastics, by causing coalescence. This is
often done by melting the workpieces and adding a filler material to
form a pool of molten material that cools to become a strong joint,
but sometimes pressure is used in conjunction with heat, or by itself,
to produce the weld.

Many different energy sources can be used for welding, including a gas
flame, an electric arc, a laser, an electron beam, friction, and
ultrasound. While often an industrial process, welding can be done in
many different environments, including open air, underwater and in
space. Regardless of location, however, welding remains dangerous, and
precautions must be taken to avoid burns, electric shock, poisonous
fumes, and overexposure to ultraviolet light.


[edit] Brazing
Main article: Brazing
Brazing is a joining process in which a filler metal is melted and
drawn into a capillary formed by the assembly of two or more work
pieces. The filler metal reacts metallurgically with the workpiece(s)
and solidifies in the capillary, forming a strong joint. Unlike
welding, the work piece is not melted. Brazing is similar to
soldering, but occurs at temperatures in excess of 450 degrees
Celsius. Brazing has the advantage of producing less thermal stresses
than welding, and brazed assemblies tend to be more ductile than
weldments because alloying elements can not segregate and precipitate.

Brazing techniques include, flame brazing, resistance brazing, furnace
brazing, diffusion brazing, and inductive brazing.


[edit] Soldering
Main article: Soldering

Soldering a printed circuit board.Soldering is a joining process that
occurs at temperatures below 449 Celsius. It is similar to brazing in
the fact that a filler is melted and drawn into a capillary to form a
join, although at a lower temperature. Because of this lower
temperature and different alloys used as fillers, the metallurgical
reaction between filler and work piece is minimal, resulting in a
weaker joint.


[edit] Preparation and validation

A combination square used for transferring designs.
[edit] Marking out
Main article: Marking out
Marking out (also known as layout) is the process of transferring a
design or pattern to a workpiece and is the first step in the
handcraft of metalworking. It is performed in many industries or
hobbies, although in the repetition industries the need to mark out
every individual piece is eliminated.

In the metal trades area, marking out consists of transferring the
engineer's plan to the workpiece in preparation for the next step,
machining or manufacture.



[edit] See also
Metalworking hand tools
Timeline of materials technology

[edit] Notes
^ Asimov, Isaac: "The Solar System and Back", page 151 ff. Doubleday
and Company,Inc. 1969.
^ Percy Knauth et al: "The Emergence of Man, The Metalsmiths", page
10-11 ff. Time-Life Books, 1974.
^ Possehl, Gregory L. (1996)

[edit] References
Possehl, Gregory L. (1996). Mehrgarh in Oxford Companion to
Archaeology, edited by Brian Fagan. Oxford University Press.

[edit] External links
Metalworking newsgroup on Usenet (alternative free web access using
Google Groups)
Metal Matters online exhibit from the Smithsonian Institution.
Society of American Silversmiths
Machinist journal News, Case studies for machinists
Modern Machine tools Machine tool Blog
Elementary Knowledge of Metalworking
[hide]v €¢ d €¢ e Metalworking

Casting · CNC · Cutting tools · Drilling and threading · Fabrication ·
Forging · Grinding · Jewellery · Lathe · Machining · Machine tooling ·
Measuring · Metalworking · Hand tools · Metallurgy · Milling ·
Occupations · Press tools · Pipe and tube bending · Smithing · Turning
· General terminology · Welding



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Categories: Metalworking | Industry | Skills
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